Fish are a natural part of the wildlife of bigger ponds.
Many animals, such as common toads, some dragonflies and some of the many species of lesser water boatmen live perfectly happily with fish. Lots of water plants don't mind fish either. And of course our native fish are wildlife themselves!
But fish can also damage ponds by
- stirring up silt, which cuts out light needed by water plants
- excreting nutrients into the water (encouraging soupy green 'blooms' of algae)
- uprooting and eating submerged water plants
- eating smaller animals.
Too many fish in small pond
Many smaller ponds naturally wouldn't have fish and these are the ponds used by plants and animals that simply don't get on with fish. So if you've got a small garden pond its often best to keep the fish out if you want to see lots of wildlife.
Problems start when people add more fish to a pond than it would have naturally. Particularly in small garden ponds, half a dozen goldfish can have a very big impact, reducing the pond to a green soup of algae.
Native fish
Ponds with natural fish populations can be fantastic, and of course ponds are important for species like the common eel (now very much less common than it once was) and the crucian carp.
Our native fish, especially crucian carp, can be threatened when other fish species are released into the wild. These problems are worse when ponds are heavily stocked with non-native fish.
Think very carefully before you release fish into any pond
It is illegal to release any fish into ponds or other waterbodies, unless you have consent from the Environment Agency or Scottish Environment Protection Agency, or the pond is in a garden with no connection to other waterbodies and the fish are not going to be able to escape.
Releasing fish into a pond used by Great Crested Newts would be inappropriate because fish are a major threat to newts, and you could end up in trouble with the law. In 2006 a man was prosecuted and fined for dumping goldfish in a river - this is a serious issue.
Angling and ponds
Angling can cause problems with protein-rich baits like ground bait, boilies and meats adding unwanted nutrients to the pond leading to algal blooms or excessive duckweed, and unregulated clearance of weed, to create swims for the fish, can affect wildlife, not to mention problems with discarded line, hooks and litter. But well-managed fishing ponds can be excellent for wildlife.
